CLC/SR 112 - Evaluation and qualification of electrical insulating materials and systems (to be defined)

IEC 62631-3-12:2024 specifies a method of test for the determination of volume resistance and volume resistivity of electrical insulation materials by applying a DC voltage. It covers casting resins described in IEC 60455-3-1, IEC 60455-3-2, IEC 60455-3-3, IEC 60455-3-4, IEC 60455-3-8 and similar products. For other specific types of materials, other standards or the general method described in IEC 62631-3-1 can be more suitable.

IEC 62631-2-3:2024 specifies the measuring technology and the test method for the relative permittivity and dielectric dissipation factor of thin single layer insulating polymer film without any additional metallization on the sample surface. The adaptive thickness range is approximately 10 μm to 100 μm. The proposed frequency is the power frequency (50 Hz or 60 Hz), and it is also suitable in the technical frequency range from 1 Hz to 1 MHz.

IEC 62836:2024 provides an efficient and reliable procedure to test the internal electric field in the insulating materials used for high-voltage applications, by using the pressure wave propagation (PWP) method. It is suitable for a planar and coaxial geometry sample with homogeneous insulating materials of thickness larger or equal to 0,5 mm and an electric field higher than 1 kV/mm, but it is also dependent on the thickness of the sample and the pressure wave generator. This first edition cancels and replaces IEC TS 62836 published in 2020. This edition includes the following significant technical changes with respect to IEC TS 62836: a) addition of Clause 12 for the measurement of space charge distribution in a planar sample; b) addition of Clause 13 for coaxial geometry samples; c) addition of Annex D with measurement examples for coaxial geometry samples; d) addition of a Bibliography; e) measurement examples for a planar sample have been moved from Clause 12 in IEC TS 62836 to Annex C.

IEC 62631-3-2:2023 describes methods of test for the determination of surface resistance and surface resistivity of electrical insulation materials by applying DC voltage. This edition includes the following significant technical changes with respect to the previous edition: a) descriptions of the electrode arrangements have been clarified; b) new descriptions of the conductive means have been added; c) a new informative Annex B summarizing the results of the comparative verification study on surface resistivities using different electrode arrangements has been added.

This part of IEC 62631 covers a method of test for the determination of volume resistance and volume resistivity of electrical insulating materials by applying a DC voltage.

This part of IEC 60216 specifies the experimental and calculation procedures for deriving the thermal endurance characteristics, temperature index (TI) and relative temperature index (RTI) of an electrical insulating material (EIM) using the "fixed time frame method (FTFM)". In this protocol, the ageing takes place for a small number of fixed times, using the appropriate number of ageing temperatures throughout each time, the properties of the specimens being measured at the end of the relevant time interval. This differs from the procedure of IEC 60216-1, where ageing is conducted at a small number of fixed temperatures, property measurement taking place after ageing times dependent on the progress of ageing. The diagnostic tests employed in the fixed time frame method are restricted to destructive tests. The method has not yet been applied to non-destructive or proof test procedures. Both the TI and the RTI determined according to the FTFM protocol are derived from experimental data obtained in accordance with the instructions of IEC 60216-1 and IEC 60216-2 as modified in this part of IEC 60216. The calculation procedures and statistical tests are modified from those of IEC 60216-3 and IEC 60216-5.

IEC 60216-5:2022 specifies the experimental and calculation procedures to be used for deriving the relative temperature index of a material from experimental data obtained in accordance with the instructions of IEC 60216-1 and IEC 60216-2. The calculation procedures are supplementary to those of IEC 60216-3. Guidance is also given for assessment of thermal ageing after a single fixed time and temperature, without extrapolation. This edition includes the following significant technical changes with respect to the previous edition:
Annex C “Computer program” has been completely reworked;
in 3.1, the terms “ATE” and “RTE” were replaced by “ATI” and “RTI” to emphasize their reference to an electrical insulating material (EIM).  This standard is to be read in conjunction with IEC 60216-1:2013, IEC 60216-2:2005 and IEC 60216-3:2021.

IEC 61857-32:2019 series is focused on applications where other possible factors need to be incorporated to evaluate any influence on the performance of the electrical insulation system (EIS). Multi-factor evaluation is the most complex type of project to design and conduct. Clear guidelines are needed to give the user of this document a uniform approach and a method to analyse the test results. This document is for applications where the stresses are some combination of other factors of influence identified in IEC 60505. The multi-factor stresses are applied during the diagnostic portion of each test cycle. A few examples of other factors of influence or multi-factor stresses are: – high vibration; – submersion in oils, water, or solutions; – voltage higher than the test voltage of the reference EIS; – decreased cold shock temperature.

This part of IEC 60544 covers ageing assessment methods which can be applied to components based on polymeric materials (e.g. cable insulation and jackets, elastomeric seals, polymeric coatings, gaiters) which are used in environments where they are exposed to radiation. The object of this standard is aimed at providing methods for the assessment of ageing in service. The approaches discussed in the following clauses cover ageing assessment programs based on condition monitoring (CM), the use of sample deposits in severe environments and sampling of real-time aged components.

This part of IEC 62631 specifies test methods for the determination of permittivity and dissipation factor properties of solid insulating materials in a high frequency range from 1 MHz to 300 MHz.

This standard describes two test methods for the evaluation of electrical insulating materials for use under severe ambient conditions at power frequencies (45 Hz to 65 Hz) by the evaluation of the resistance to tracking and erosion, using a liquid contaminant and inclined plane specimens. The two methods are: - Method 1: test at constant voltage, - Method 2: test at stepwise increased voltage. Method 1 is the most widely used method as there is less need for continual inspection. The test conditions are designed to accelerate the production of the effects, but do not reproduce all the conditions encountered in service.

This part of IEC 62631 covers procedures for the determination of insulation resistance and volume resistivity of insulating materials by applying DC-voltage and temperatures up to 800 °C. The typical application materials include high temperature mica plate and alumina ceramics.

IEC 60216-3:2021 is available as IEC 60216-3:2021 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.IEC 60216-3:2021 specifies the calculation procedures used for deriving thermal endurance characteristics from experimental data obtained in accordance with the instructions of IEC 60216-1 and IEC 60216-2, using fixed ageing temperatures and variable ageing times. The experimental data can be obtained using non-destructive, destructive or proof tests. Data obtained from non-destructive or proof tests can be incomplete, in that it is possible that measurement of times taken to reach the end-point will have been terminated at some point after the median time but before all specimens have reached end-point. The procedures are illustrated by worked examples, and suitable computer programs are recommended to facilitate the calculations. This edition includes the following significant technical changes with respect to the previous edition: - a new computer program has been included; - Annex E " has been completely reworked.

IEC 62631-2-1:2018 describes test methods for the determination of permittivity and dissipation factor properties of solid insulating materials (AC methods from 0,1 Hz up to 10 MHz). This first edition cancels and replaces the first edition IEC 60250, published in 1969. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a. technical frequencies confined to AC methods; b. update on measurements on solid dielectric materials.

IEC 62631-3-11:2018 covers a method of test for the determination of volume resistance and volume resistivity of electrical insulation materials by applying DC voltage. It covers the materials described in IEC 60455-3-5, IEC 60464-3-1, IEC 60464-3-2 and similar products.

IEC 60112:2020 specifies the method of test for the determination of the proof and comparative tracking indices of solid insulating materials on pieces taken from parts of equipment and on plaques of material using alternating voltage. This document provides a procedure for the determination of erosion when required. This test method evaluates the composition of the material as well as the surface of the material being evaluated. Both the composition and surface condition directly influence the results of the evaluation and are considered when using the results in material selection process. Test results are not directly suitable for the evaluation of safe creepage distances when designing electrical apparatus. This basic safety publication focusing on a safety test method is primarily intended for use by technical committees in the preparation of safety publications in accordance with the principles laid down in IEC Guide 104 and lSO/lEC Guide 51. This edition includes the following significant technical changes with respect to the previous edition:  
Introduction of a new contaminant, solution C with a surfactant aligned with the test method of IEC 60587. The definition of the solution B was transferred to Annex B for backward reference.
Introduction of a screening test, considering the fact that some materials can withstand high test voltages, but fail at lower test voltages.  It has the status of a basic safety publication in accordance with IEC Guide 104.

IEC 61857-31:2017(E) establishes an EIS evaluation for applications with a designed life of 5 000 h or less. This test method follows the procedures of IEC 60505 and is modified based on the range of designed life.

IEC 62631-3-1:2016 covers a method of test for the determination of volume resistance and volume resistivity of electrical insulation materials by applying a DC voltage. This edition includes the following significant technical changes with respect to the second edition of IEC 60093: a) IEC 60093 has been completely revised, both editorially and technically, and incorporated into the new IEC 62631 series; b) test methods have been updated to current day state of the art; c) volume and surface resistance and resistivity are now separated to appear in this part of IEC 62631 and in IEC 62631-3-2, respectively.

IEC 62631-3-3:2015 covers methods of test for the determination of the insulation resistance of electrical insulating materials or insulating systems by applying DC voltage. This first edition cancels and replaces the first edition of IEC 60167, published in 1964, and constitutes a technical revision. This edition includes the following significant technical changes with respect to the first edition of IEC 60167: a) IEC 60167 has been completely revised, both editorially and technically, and incorporated into the new IEC 62631 series; b) test methods have been updated to current day state of the art.

IEC 62631-3-2:2015 covers methods of test for the determination of surface resistance and surface resistivity of electrical insulation materials by applying DC voltage. This first edition cancels and replaces the second edition of IEC 60093, published in 1980, and constitutes a technical revision. This edition includes the following significant technical changes with respect to the second edition of IEC 60093: a) IEC 60093 has been completely revised, both editorially and technically, and incorporated into the new IEC 62631 series; b) test methods have been updated to current day state of the art; c) volume and surface resistance and resistivity are now separated into IEC 62631-3-1 and IEC 62631-3-2, respectively.

IEC 61251:2015 describes many of the factors involved in voltage endurance tests on electrical insulating materials and systems. It describes the voltage endurance graph, lists test methods illustrating their limitations and gives guidance for evaluating the sinusoidal a.c. voltage endurance of insulating materials and systems from the results of the tests. This International Standard is applicable over the voltage frequency range 20 Hz to 1 000 Hz. The general principles can also be applicable to other voltage shapes, including impulse voltages. The terminology to be used in voltage endurance is defined and explained. This first edition of IEC 61251 cancels and replaces the second edition of IEC TS 61251, published in 2008. This edition constitutes a technical revision and includes the following significant technical changes with respect to the second edition of IEC TS 61251: a) upgrade from Technical Specification to an International Standard; b) clarification of issues raised since publication of IEC TS 61251.

IEC corrigendum

IEC 61858-1:2014 lists the required test procedures for qualification of modifications of an established electrical insulation system (EIS) with respect to its thermal classification. This standard is applicable to EIS used in wire-wound winding electrotechnical devices. The test procedures are comparative in that the performance of a candidate EIS is compared to that of a reference EIS, which has proven service experience in accordance with IEC 60505 or has been evaluated by one of the procedures given in the IEC 61857 series. This first edition of IEC 61858-1 cancels and replaces the third edition of IEC 61858, published in 2008. It constitutes a technical and editorial revision. This edition includes the following significant technical changes with respect to the previous edition: a) this part is specifically for wire-wound winding EIS; b) new figures and charts support the contents.

IEC 61858-2:2014 lists the required test procedures for qualification of modifications of an established electrical insulation system (EIS) with respect to its thermal classification. This standard is applicable to EIS used in form-wound electrotechnical devices. The test procedures are comparative in that the performance of a candidate EIS is compared to that of a reference EIS, which has proven service experience in accordance with IEC 60505 or has been evaluated by one of the procedures given in IEC 60085 and IEC 60034-18-31.

IEC 60243-2:2013 gives requirements additional to those in IEC 60243-1 for the determination of the electric strength of solid insulating materials under direct voltage stress. This third edition cancels and replaces the second edition published in 2001, and constitutes an editorial revision.

IEC 60544-1:2013 deals broadly with the aspects to be considered in evaluating the effects of ionizing radiation on all types of organic insulating materials. It also provides, for X-rays, gamma-rays, and electrons, a guide to dosimetry terminology, methods for dose measurements, testing carried out at irradiation facilities, evaluation and testing of material characteristics and properties, documenting the irradiation process. This edition includes the following significant technical changes with respect to the previous edition: a) recent advances in simulation methods of radiation interaction with different matter enables the prediction of the energy-deposition profile in matter and design the irradiation procedure; b) many new dosimetry systems have become available.

IEC 60243-1:2013 provides test methods for the determination of short-time electric strength of solid insulating materials at power frequencies between 48 Hz and 62 Hz. This standard does not cover the testing of liquids and gases, although these are specified and used as impregnates or surrounding media for the solid insulating materials being tested. NOTE: Methods for the determination of breakdown voltages along the surfaces of solid insulating materials are included.

IEC 60216-8:2013 specifies the general ageing conditions and simplified procedures to be used for deriving thermal endurance characteristics, which are shown by temperature index (TI) and/or relative temperature index (RTI) and the halving interval (HIC). The procedures specify the principles for evaluating the thermal endurance properties of materials exposed to elevated temperature for long periods. In the application of this standard, it is assumed that a practically linear relationship exists between the logarithm of the time required to cause the predetermined property change and the reciprocal of the corresponding absolute temperature (Arrhenius relationship). For the valid application of the standard, no transition, in particular no first-order transition should occur in the temperature range under study.

IEC 60216-1:2013 specifies the general ageing conditions and procedures to be used for deriving thermal endurance characteristics and gives guidance in using the detailed instructions and guidelines in the other parts of the standard. Although originally developed for use with electrical insulating materials and simple combinations of such materials, the procedures are considered to be of more general applicability and are widely used in the assessment of materials not intended for use as electrical insulation. In the application of this standard, it is assumed that a practically linear relationship exists between the logarithm of the time required to cause the predetermined property change and the reciprocal of the corresponding absolute temperature (Arrhenius relationship). For the valid application of the standard, no transition, in particular no first-order transition should occur in the temperature range under study. This sixth edition cancels and replaces the fifth edition, published in 2001. It constitutes an editorial revision where the simplified method has been removed and now forms Part 8 of the IEC 60216 series: Instructions for calculating thermal endurance characteristics using simplified procedures.

IEC 62068:2013 applies to electrical equipment, regardless of voltage, containing an insulation system, which is: - connected to an electronic power supply, and - requires an evaluation of insulation endurance under repetitive voltage impulses. This standard proposes a general test procedure to facilitate screening of electrical insulating materials (EIM) and systems (EIS) and to achieve a relative evaluation of insulation endurance under conditions of repetitive impulses. This first edition of IEC 62068 replaces IEC 62068-1:2003. It has been re-numbered as IEC 62068, as decided at the Plenary Meeting of TC 112 in Prague 2011. The main changes with regard to IEC 62068-1:2003 concern the terms and definitions which are now aligned, in part, on IEC/TS 61934 and IEC/TS 60034-18-42.

IEC 60544-2:2012 specifies the controls maintained over the exposure conditions during and after the irradiation of insulating materials with ionizing radiation prior to the determination of radiation-induced changes in physical or chemical properties. This standard specifies a number of potentially significant irradiation conditions as well as various parameters which can influence the radiation-induced reactions under these conditions. The objective of this standard is to emphasize the importance of selecting suitable specimens, exposure conditions and test methods for determining the effect of radiation on appropriately chosen properties. Since many materials are used either in air or in inert environments, standard exposure conditions are recommended for both of these situations. It should be noted that this standard does not consider measurements which are performed during the irradiation. This edition includes the following significant technical changes with respect to the previous edition: - alignment with standards recently developed by SC 45A as well as with other parts in the IEC 60544 series.

IEC 60544-5:2011 covers ageing assessment methods which can be applied to components based on polymeric materials (e.g. cable insulation and jackets, elastomeric seals, polymeric coatings, gaiters) which are used in environments where they are exposed to radiation. The object of this standard is aimed at providing methods for the assessment of ageing in service. The approaches discussed in the following clauses cover ageing assessment programmes based on condition monitoring (CM), the use of sample deposits in severe environments and sampling of real-time aged components. This second edition cancels and replaces the first edition, published in 2003, and constitutes an editorial revision to align it with standards recently developed by SC 45A as well as with other parts in the IEC 60544 series.

IEC 60505:2011 establishes the basis for estimating the ageing of electrical insulation systems (EIS) under conditions of either electrical, thermal, mechanical, environmental stresses or combinations of these (multifactor stresses). It specifies the principles and procedures that shall be followed, during the development of EIS functional test and evaluation procedures, to establish the estimated service life for a specific EIS. This standard should be used by all IEC technical committees responsible for equipment having an EIS. The main change with respect to the previous edition is that Annex A: Glossary is now available in an Internet version as well as a hardcopy version. The internet version contains an abridged text version and a multimedia supplement.

IEC 62631-1:2011 gives general guidelines for the determination of dielectric and resistive properties of solid electrical insulating materials.

IEC 60243-3:2013 gives requirements additional to those in IEC 60243-1 for the determination of the electric strength of solid insulating materials under 1,2/50 µs impulse voltage stress. This third edition cancels and replaces the second edition, published in 2001, and constitutes an editorial revision.

IEC 60212:2010 gives the accepted conditions of exposure time, temperature, atmospheric humidity and liquid immersion for use in testing solid electrical insulating materials. The range is sufficiently wide to enable suitable conditions to be selected so that either of the primary objects, set out below as a) and b), of conditioning can be achieved. These objectives aim to obtain greater reproducibility of test results by: a) partly counteracting the variations of the properties of the material due to the past history of the test specimens (often known as 'normalizing', here called preconditioning), and b) ensuring uniformity of conditions during the testing. This standard is not intended to be applied for determining the influence of exposure to certain temperatures and humidity or immersions in liquids, on the properties of a material. Procedures pertaining to the effect of an environment on a material are given in various parts of IEC 60068. The significant technical changes with respect to the previous edition are as follows: - the scope and normative references have been updated and terms and definitions completely reviewed; - technical details in Table 2 have been aligned to today's usage.

IEC 61857-21:2009 describes a general-purpose model (GPM) and a tall channel alternative model (GPM-TC) which can be used for the evaluation of wire-wound electrical insulation systems (EIS) where specific electrotechnical products are not available or required. The third edition cancels and replaces the second edition published in 2004, and constitutes editorial revisions to make this standard compatible with Parts 1 and 22.

IEC 61857-1:2008 specifies a general test procedure for the thermal evaluation and qualification of electrical insulation systems (EIS) and establishes a procedure that compares the performance of a candidate EIS to that of a reference EIS. This standard is applicable to existing or proposed EIS used in electrotechnical products with an input voltage of up to 1 000 V where the thermal factor is the dominating ageing factor. This third edition cancels and replaces the second edition published in 2004, and constitutes editorial revisions to make this standard compatible with Parts 21 and 22.

IEC 61857-22:2008 provides a general-purpose procedure for the evaluation of wire-wound systems using a general purpose encapsulated-coil model (ECM) where the application is unknown. This second edition cancels and replaces the first edition published in 2002, and constitutes editorial revisions to make this standard compatible with Parts 1 and 21.

IEC 60216-5 specifies the experimental and calculation procedures to be used for deriving the relative thermal endurance index of a material from experimental data obtained in accordance with the instructions of IEC 60216-1 and IEC 60216-2. The calculation procedures are supplementary to those of IEC 60216-3. Guidance is also given for assessment of thermal ageing after a single fixed time and temperature, without extrapolation. The experimental data may in principle be obtained using destructive, non-destructive or proof tests, although destructive tests have been much more extensively employed. Data obtained from non-destructive or proof tests may be 'censored', in that measurement of times taken to reach the endpoint may have been terminated at some point after the median time but before all specimens have reached end-point (see IEC 60216-1). Guidance is given for preliminary assignment of a thermal class for an insulating material, based upon the thermal ageing performance. The calculation procedures of this standard also apply to the determination of the thermal class of an electrical insulation system when the thermal stress is the prevailing ageing factor. This third edition clarifies and corrects a few items and adds an Annex D which provides criteria for the selection of the reference (or reference EIM). The third edition provides instructions for deriving a provisional estimate of the temperature up to which a material may give satisfactory performance in an application (by comparative thermal ageing with a material of known performance).

IEC 60085:2007 now distinguishes between thermal classes for electrical insulation systems and electrical insulating materials. It establishes the criteria for evaluating the thermal endurance of either electrical insulating materials (EIM) or electrical insulation systems (EIS). It also establishes the procedure for assigning thermal classes. This standard is applicable where the thermal factor is the dominant ageing factor. The major technical changes with regard to the previous edition concern the fact that this edition is an amalgamation of the third edition of this standard together with IEC 62114:2001. It has the status of a horizontal standard in accordance with IEC Guide 108.

Describes two test methods for the evaluation of electrical insulating materials for use under severe ambient conditions at power frequencies (45 Hz to 65 Hz) by measurement of the resistance to tracking and erosion, using a liquid contaminant and inclined plane specimens. The two methods are as follows: - Method 1: constant tracking voltage; - Method 2: stepwise tracking voltage. The main changes from the previous edition are as follows: experience has indicated the need for improved description of the experimental method. For the preparation of the test specimens abrasion is recommended only if necessary. The ventilation of the test chamber is described in detail. For specimens of soft elastomeric materials a mounting support is described. The maximum depth of erosion has to be reported in the classification.

Amandma A1:2008 je dodatek k standardu SIST EN 60450:2005
Describes a standardized method for the determination of the average viscometric degree of polymerization (DPv) of new and aged cellulosic electrically insulating materials. It may be applied to all cellulosic insulating materials such as those used in transformer, cable or capacitor manufacturing. The methods described can also be used for the determination of the intrinsic viscosity of solutions of chemically modified kraft papers, provided that these dissolve completely in the selected solvent. Caution should be taken if the method is applied to loaded kraft papers. Note: Within a sample of material, all the cellulose molecules do not have the same degree of polymerization so that the mean value measured by viscometric methods is not necessarily the same as that which may be obtained by, for instance, osmotic or ultra centrifuging methods. Experience has indicated the need for improved description of the experimental method. It describes a revised procedure that overcomes the limitations of the first edition.

Determines the ability of insulating materials to produce electrolytic corrosion on metals being in contact with them under the influence of electric stress, high humidity and elevated temperature. The effect of electrolytic corrosion is assessed in one test by using consecutively two methods: - visual semi-quantitative method consisting in comparing visually the corrosion appearing on the anode and cathode metal strips, with those given in the reference figures. This method consists of the direct visual assessment of the degree of corrosion of two copper strips, acting as anode and cathode respectively, placed in contact with the tested insulating material under a d.c. potential difference at specified environmental conditions. The degree of corrosion is assessed by visually comparing the corrosion marks on the anode and cathode metal strips with those shown in the reference figures; - quantitative method, which involves the tensile strength measurement, carried out on the same anode and cathode metal strips after visual inspection. An additional quantitative test method for determining electrolytic corrosion, which involves tensile strength measurement of copper wire, is described in the informative Annex C. The main changes with respect to the previous edition are listed below: - experience has indicated the need for improved description of the experimental method. It describes a revised procedure for the visual and tensile strength test method that overcomes the limitations of the first edition; - one older method of the first edition has partly been maintained in the informative annex.

Specifies the experimental and calculation procedures for deriving the thermal endurance characteristics, temperature index (TI) and relative thermal endurance index (RTE) of a material using the 'fixed time frame method (FTFM)'. In this protocol, the ageing takes place for a small number of fixed times, using the appropriate number of ageing temperatures throughout each time, the properties of the specimens being measured at the end of the relevant time interval. This differs from the procedure of IEC 60216-1, where ageing is conducted at a small number of fixed temperatures, property measurement taking place after ageing times dependent on the progress of ageing. The diagnostic tests employed in the fixed time frame method are restricted to destructive tests. The method has not as yet been applied to non-destructive or proof test procedures. Both the TI and the RTE determined according to the FTFM protocol are derived from experimental data obtained in accordance with the instructions of IEC 60216-1 and IEC 60216-2 as modified in this standard. The calculation procedures and statistical tests are modified from those of IEC 60216-3 and IEC 60216-5. The significant technical changes with respect to the previous edition are as follows. - This new edition has been supplemented by Annex G and the corresponding software.

Covers minimum requirements for ventilated and electrically heated single-chamber ovens, with or without forced gas circulation, for thermal endurance evaluation of electrical insulation. It covers ovens designed to operate over all or part of the temperature range from 20 °C above ambient to 500 °C. It gives acceptance tests and in-service monitoring tests for these ageing ovens. The main changes with regard to the previous edition is that this edition adapts IEC 60216-4-1 to the technical content and the editorial form of IEC 60216-4-2 and IEC 60216-4-3. In addition, errors and omissions in the third edition have been corrected.

Gives guidance for the choice of test criteria for the determination of thermal endurance characteristics. It includes a list of existing published procedures which is however not exhaustive. The main changes from the previous edition are as follows: - editorial, - Table 1 has been actualized essentially by Part 3 sheets of SC 15C publications.

Describes a standardized method for the determination of the average viscometric degree of polymerization (DPv) of new and aged cellulosic electrically insulating materials. It may be applied to all cellulosic insulating materials such as those used in transformer, cable or capacitor manufacturing. The methods described can also be used for the determination of the intrinsic viscosity of solutions of chemically modified kraft papers, provided that these dissolve completely in the selected solvent. Caution should be taken if the method is applied to loaded kraft papers. Note: Within a sample of material, all the cellulose molecules do not have the same degree of polymerization so that the mean value measured by viscometric methods is not necessarily the same as that which may be obtained by, for instance, osmotic or ultra centrifuging methods. Experience has indicated the need for improved description of the experimental method. It describes a revised procedure that overcomes the limitations of the first edition.